The temperatures and processing times used when canning vegetables and fruit are determined by many factors. The food acidity, how the jars are packed, and canning method being used all determine the processing time, temperatures, and PSI when canning. The information below will help explain some of the factors that need to be considered when canning.

Canning - Food Acidity

There are two basic methods for canning, boiling-water-bath and pressure canning. The method used is normally determined by whether the food being canned has a high acidity level or a low acidity level.

High-Acid Foods: In high-acid foods, such as tomatoes, fruit and pickles, the growth of the Clostridium botulinum bacteria, which is heat resistant, is prevented by the high acidity level or the acidity allows the botulism spores to be destroyed quicker when boiled. This allows them to be processed using a boiling-water-bath at 212°F. The most common forms of spoilage microorganisms in acid foods are mold and yeast, which are destroyed by the boiling-water-bath.

Tomatoes generally have an acidity level that is high enough to be considered an acid food but there are some varieties that have an acidity level that is slightly under the level required. Tomatoes that have a slightly lower acidity level can be made acidic by adding lemon juice or citric acid. The USDA suggests adding lemon juice or citric acid to all tomatoes to ensure acidity levels. They are then safe to process using the boiling-water-bath.

Low-Acid Foods: Low-acid foods, such as vegetables, seafood, meats, and poultry must be pressure canned at 240°F to eliminate and prevent the growth of bacteria called Clostridium botulinum. The botulinum spores are very resistant to heat so processing at the higher temperatures provides a way to destroy these spores. If the low acid foods were processed in a boiling-water-bath canner, they would have to be processed for a length of time ranging from 7 to 12 hours. Processed at the 240° to 250°F using a pressure canner takes 20 to 100 minutes, depending on the type of food, size of jars, and the way it is packed.

The chart below shows which foods are considered high acidity and which are low acidity.

High Acidity Foods

Using Boiling-Water Bath orPressure Canning (for less processing)

Low Acidity Foods

Using Pressure Canning Only

Apples

Plums

Artichokes (Jerusalem)

Mushrooms

Apricots

Raspberries

Asparagus

Okra

Blackberries

Rhubarb

Beans (green or yellow)

Parsnips

Blueberries

Strawberries

Beets

Peas

Cranberries

Pineapple

Broccoli

Peas (snap)

Cherries

Tomatoes (with acid added)

Brussels Sprouts

Peppers

Cucumbers (pickled)

Cabbage

Potatoes

Grapefruit

Carrots

Pumpkin

Grapes

Cauliflower

Spinach

Nectarines

Corn

Squash (summer)

Oranges

Eggplant

Squash (winter)

Peaches

Figs

Sweet Potatoes

Pears

Lima Beans

Canning - Temperatures and Processing Times

Using the proper processing temperature and time is very important when canning foods to ensure that the processed food will be safe to eat. If not processed properly the food will spoil. There are several factors that affect the amount of processing time required. Some of these factors are listed below:

The size and shape of the jars. Less time is needed for smaller jars.

Whether they have been raw packed or hot packed.

The amount of liquid in the jars. More liquid will allow the jar contents to heat more quickly.

The size of the food being processed. Smaller pieces will heat faster.

The canning method being used. Pressure canning will be faster.

The altitude in your area. See at the bottom of each chart for instructions on how much to adjust the processing time for altitudes above sea level.

All of these factors determine the canning method, processing time and PSI (pounds per square inch) of pressure to be used. Be sure to follow all canning instructions very carefully. It is important to adjust the processing times when you are at a higher elevation. At sea level, water boils at 212°F but as the elevation increases water will boil at lower temperatures. The temperatures at which water boils at the higher elevations are not sufficient for killing bacteria. To compensated for the lower boiling temperatures, the processing time for boiling-water-bath canning needs to be increased and for pressure canning the PSI needs to be increased to destroy the harmful bacteria. Shown below are some charts with processing information and the adjustments that need to be made in processing time for higher elevations. If you are unsure of what the elevation is in your area, you can call your local county extension office to request this information.

The processing times above are for canning at sea level. Adjust as shown below:

Processing Time atSea Level

Adjusted Processing Time

20 Minutes or Less

Add 1 minute per 1000 ft. in elevation

Over 20 Minutes

Add 2 minutes per 1000 ft. in elevation.

When using a pressure canner to process high acid foods, your processing time is much shorter than when processing with the boiling-water-bath. When processing at higher elevations the processing time can remain the same as what is used at sea level but the PSI (pounds per square inch) needs to be increased to make up for the lower internal temperature of the canner. Do not begin counting the processing time until the canner has reached its required pressure reading.

High Acid Foods - Dial Gauge Pressure Canning Method

Headspace:

Leave 1/2 inch headspace on all high acid foods listed below. At higher elevations, the steam in the headspace will expand more than at elevations below 1000 feet. To allow for this expansion, it is suggested that you increase the headspace by 1/8 inch for each 1000 feet above see level, not to exceed 1 inch on pint jars and 1 3/4 inches on quart jars.

Food Type

Pack Method

Process Time(minutes)

PSI(pounds per square inch of pressure)

Pint Jars

Quart Jars

Under2000 ft.

2001 to 4000 ft.

4001 to 6000 ft.

6001 to 8000 ft.

Apples

Hot

8

8

6 lb.

7 lb.

8 lb.

9 lb.

Apricots

RawHot

1010

1010

6 lb.6 lb.

7 lb.7 lb.

8 lb.8 lb.

9 lb.9 lb.

Blackberries

RawHot

88

108

6 lb.6 lb.

7 lb.7 lb.

8 lb.8 lb.

9 lb.9 lb.

Blueberries

RawHot

88

108

6 lb.6 lb.

7 lb.7 lb.

8 lb.8 lb.

9 lb.9 lb.

Cherries

RawHot

108

1010

6 lb.6 lb.

7 lb.7 lb.

8 lb.8 lb.

9 lb.9 lb.

Grapefruit

RawHot

810

1010

6 lb.6 lb.

7 lb.7 lb.

8 lb.8 lb.

9 lb.9 lb.

Nectarines

RawHot

1010

1010

6 lb.6 lb.

7 lb.7 lb.

8 lb.8 lb.

9 lb.9 lb.

Oranges

RawHot

810

1010

6 lb.6 lb.

7 lb.7 lb.

8 lb.8 lb.

9 lb.9 lb.

Peaches

RawHot

1010

1010

6 lb.6 lb.

7 lb.7 lb.

8 lb.8 lb.

9 lb.9 lb.

Pears

Hot

10

10

6 lb.

7 lb.

8 lb.

9 lb.

Plums

RawHot

1010

1010

6 lb.6 lb.

7 lb.7 lb.

8 lb.8 lb.

9 lb.9 lb.

Raspberries

RawHot

88

108

6 lb.6 lb.

7 lb.7 lb.

8 lb.8 lb.

9 lb.9 lb.

Rhubarb

Hot

8

8

6 lb.

7 lb.

8 lb.

9 lb.

Tomatoes - Juice (with acid added)

Hot

20

20

6 lb.

7 lb.

8 lb.

9 lb.

Hot

15

15

11 lb.

12 lb.

13 lb.

14 lb.

Tomatoes - Whole or halved - No Liquid Added (with acid added)

Raw

40

40

6 lb.

7 lb.

8 lb.

9 lb.

Raw

25

25

11 lb.

12 lb.

13 lb.

14 lb.

Tomatoes - Crushed (Quartered) - No Liquid Added (with acid added)

Hot

20

20

6 lb.

7 lb.

8 lb.

9 lb.

Hot

15

15

11 lb.

12 lb.

13 lb.

14 lb.

Weighted-Gauge Pressure Canning:

When using a weighted-gauge pressure canner, use the chart above for pack methods and processing time. Weighted-gauge pressure canners cannot have the PSI increased by 1 lb. increments, so adjust the PSI as shown below:

PSI from Chart Above

Weighted-Gauge PSI Setting

PSI of 6 lb. to 9 lb.

10 PSI

PSI of 11 lb. to 14 lb.

15 PSI

Elevations under 1000 ft.

5 PSI

Low Acid Foods - Dial Gauge Pressure Canning Method

Headspace:

Leave 1 inch headspace on all low acid foods listed below with the exception of lima beans, raw packed. When using the raw packed method for canning with quart size jars, increase the headspace to 1 1/2 inches for small beans and 1 1/4 inches for large beans.

At higher elevations, the steam in the headspace will expand more than at elevations below 1000 feet. To allow for this expansion, it is suggested that you increase the headspace by 1/8 inch for each 1000 feet above see level, not to exceed 1 inch on pint jars and 1 3/4 inches on quart jars.

Food Type

Pack Method

Process Time (minutes)

PSI(pounds per square inch of pressure)

Pint Jars

Quart Jars

Under2000 ft.

2001 to 4000 ft.

4001 to 6000 ft.

6001 to 8000 ft.

Artichokes (Jerusalem)

Hot

25

25

11 lb.

12 lb.

13 lb.

14 lb.

Asparagus

RawHot

3030

4040

11 lb.11 lb.

12 lb.12 lb.

13 lb.13 lb.

14 lb.14 lb.

Beans (green or yellow)

RawHot

2020

2525

11 lb.11 lb.

12 lb.12 lb.

13 lb.13 lb.

14 lb.14 lb.

Beets

Hot

30

35

11 lb.

12 lb.

13 lb.

14 lb.

Broccoli

Canning is not recommended. Best to freeze orpickle for preservation.

Brussels Sprouts

Canning is not recommended. Best to freeze orpickle for preservation.

Cabbage

Canning is not recommended. Best kept in cold storage.

Carrots

RawHot

2525

3030

11 lb.11 lb.

12 lb.12 lb.

13 lb.13 lb.

14 lb.14 lb.

Cauliflower

Canning is not recommended. Best to freezefor preservation.

Corn

RawHot

5555

8585

11 lb.11 lb.

12 lb.12 lb.

13 lb.13 lb.

14 lb.14 lb.

Eggplant

Canning is not recommended.

Lima Beans

RawHot

4040

5050

11 lb.11 lb.

12 lb.12 lb.

13 lb.13 lb.

14 lb.14 lb.

Mushrooms

Hot

45

11 lb.

12 lb.

13 lb.

14 lb.

Okra

RawHot

2525

4040

11 lb.11 lb.

12 lb.12 lb.

13 lb.13 lb.

14 lb.14 lb.

Peas

RawHot

4040

4040

11 lb.11 lb.

12 lb.12 lb.

13 lb.13 lb.

14 lb.14 lb.

Peas (snap)

Canning is not recommended. Best to freezefor preservation.

Peppers

Hot

35

11 lb.

12 lb.

13 lb.

14 lb.

Potatoes, White

Hot

35

40

11 lb.

12 lb.

13 lb.

14 lb.

Pumpkin

Hot

55

90

11 lb.

12 lb.

13 lb.

14 lb.

Spinach and Other Greens

Hot

70

90

11 lb.

12 lb.

13 lb.

14 lb.

Squash (summer)

Canning is not recommended. Best eaten fresh.

Squash (winter)

Hot

55

90

11 lb.

12 lb.

13 lb.

14 lb.

Sweet Potatoes

Hot

65

90

11 lb.

12 lb.

13 lb.

14 lb.

Weighted-Gauge Pressure Canning:

When using a weighted-gauge pressure canner, use the chart above for pack methods and processing time. Weighted-gauge pressure canners cannot have the PSI increased by 1 lb. increments, so adjust the PSI as shown below: